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Registros recuperados: 9
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A Lagrangian Method to Isolate the Impacts of Mixed Layer Subduction on the Meridional Overturning Circulation in a Numerical Model ArchiMer
Thomas, Matthew; Treguier, Anne-marie; Blanke, Bruno; Deshayes, Julie; Voldoire, Aurore.
Large differences in the Atlantic meridional overturning circulation (AMOC) exhibited between the available ocean models pose problems as to how they can be interpreted for climate policy. A novel Lagrangian methodology has been developed for use with ocean models that enables a decomposition of the AMOC according to its source waters of subduction from the mixed layer of different geographical regions. The method is described here and used to decompose the AMOC of the Centre National de Recherches Météorologiques (CNRM) ocean model, which is approximately 4.5 Sv (1 Sv = 106 m3 s−1) too weak at 26°N, compared to observations. Contributions from mixed layer subduction to the peak AMOC at 26°N in the model are dominated by the Labrador Sea, which contributes...
Tipo: Text Palavras-chave: Circulation; Dynamics; Convection; Lagrangian circulation; Transport; Meridional overturning circulation; Atm; Ocean Structure; Phenomena; Oceanic mixed layer; Models and modeling; General circulation models.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00284/39523/38016.pdf
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Cyclones and Anticyclones in Seismic Imaging ArchiMer
Barbosa Aguiar, A. C.; Menesguen, Claire; Le Gentil, Sylvie; Schopp, Richard; Carton, Xavier.
Nearly all the subsurface eddies detected in seismic imaging of sections in the northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MW cyclones have been observed and studied. In this study, the work of previous numerical studies is extended to investigate some characteristics of layering surrounding MW cyclones, using a primitive equation model with equal diffusivities for salinity and temperature to suppress the effects of double diffusion. It is shown that, after a stable state is reached, both anticyclones and cyclones display similar patterns of layering: stacked thin layers of high acoustic reflectivity located above and below the core of each vortex, which do not match isopycnals. The authors conclude...
Tipo: Text Palavras-chave: Geographic location/entity; North Atlantic Ocean; Circulation/ Dynamics; Small scale processes; Atm/Ocean Structure/ Phenomena; Eddies; Vortices; Observational techniques and algorithms; Acoustic measurements/effects; Models and modeling; Primitive equations model.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00281/39190/37746.pdf
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Global Air-Sea CO2 Flux in 22 CMIP5 Models: Multiyear Mean and Interannual Variability* ArchiMer
Dong, Fang; Li, Yangchun; Wang, Bin; Huang, Wenyu; Shi, Yanyan; Dong, Wenhao.
To assess the capability of the latest Earth system models (ESMs) in representing historical global air-sea CO2 flux, 22 models from phase 5 of the Coupled Model Intercomparision Project (CMIP5) are analyzed, with a focus on the spatial distribution of multiyear mean and interannual variability. Results show that the global distribution of air-sea CO2 flux is reasonable in most of the models and that the main differences between models and observationally based results exist in regions with strong vertical movement. The annual mean flux in the 18-member multimodel ensemble (MME; four models were excluded because of their poor performances) mean during 1996-2004 is 1.95 Pg C yr(-1) (1 Pg = 10(15) g; positive values mean into the ocean), and all but one...
Tipo: Text Palavras-chave: Interannual variability; Model output statistics; Model comparison; Variability; Models and modeling; Ocean models; Ensembles; Climate models.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00383/49421/49858.pdf
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QuasiGeostrophic Diagnosis of Mixed-Layer Dynamics Embedded in a Mesoscale Turbulent Field ArchiMer
Chavanne, Cedric P.; Klein, Patrice.
A quasigeostrophic model is developed to diagnose the three-dimensional circulation, including the vertical velocity, in the upper ocean from high-resolution observations of sea surface height and buoyancy. The formulation for the adiabatic component departs from the classical surface quasigeostrophic framework considered before since it takes into account the stratification within the surface mixed layer that is usually much weaker than that in the ocean interior. To achieve this, the model approximates the ocean with two constant stratification layers: a finite-thickness surface layer (or the mixed layer) and an infinitely deep interior layer. It is shown that the leading-order adiabatic circulation is entirely determined if both the surface...
Tipo: Text Palavras-chave: Circulation; Dynamics; Ageostrophic circulations; Mesoscale processes; Ocean dynamics; Vertical motion; Models and modeling; Diagnostics; Quasigeostrophic models.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00309/42031/41330.pdf
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Reconstructability of 3-Dimensional Upper Ocean Circulation from SWOT Sea Surface Height Measurements ArchiMer
Qiu, Bo; Chen, Shuiming; Klein, Patrice; Ubelmann, Clement; Fu, Lee-lueng; Sasaki, Hideharu.
Utilizing the framework of effective surface quasi-geostrophic (eSQG) theory, we explored the potential of reconstructing the 3D upper ocean circulation structures, including the balanced vertical velocity (w) field, from high-resolution sea surface height (SSH) data of the planned SWOT satellite mission. Specifically, we utilized the 1/30°, submesoscale-resolving, OFES model output and subjected it through the SWOT simulator that generates the along-swath SSH data with expected measurement errors. Focusing on the Kuroshio Extension region in the North Pacific where regional Rossby numbers range from 0.22 to 0.32, we found that the eSQG dynamics constitutes an effective framework for reconstructing the 3D upper ocean circulation field. Using the modeled...
Tipo: Text Palavras-chave: Variability; Models and modeling; General circulation models; Vertical motion; Circulation/ Dynamics; Quasigeostrophic models; Mesoscale processes; Observational techniques and algorithms; Oceanic variability; Altimetry.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00309/42032/41331.pdf
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Response of North-Atlantic Ocean circulation to atmospheric weather regimes ArchiMer
Barrier, Nicolas; Cassou, Christophe; Deshayes, Julie; Treguier, Anne-marie.
A new framework is proposed for investigating the atmospheric forcing of North-Atlantic ocean circulation. Instead of using classical modes of variability, such as the North-Atlantic Oscillation (NAO) or the East-Atlantic Pattern, we here use the weather regimes paradigm. Using this framework we avoid problems associated with the assumptions of orthogonality and symmetry that are particular to modal analysis and known to be unsuitable for the NAO. Using ocean-only historical and sensitivity experiments, we investigate the impacts of the four winter weather regimes on horizontal and overturning circulations. Our results suggest that the Atlantic Ridge (AR), NAO− and NAO+ regimes induce a fast (monthly to interannual timescales) adjustment of the gyres via...
Tipo: Text Palavras-chave: Circulation; Dynamics; Meridional overturning circulation; Atm; Ocean Structure; Phenomena; Gyres; North Atlantic Oscillation; Wind; Physical Meteorology and Climatology; Climate classification; Regimes; Models and modeling; Ocean models.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00161/27258/25467.pdf
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Seasonal Mesoscale and Submesoscale Eddy Variability along the North Pacific Subtropical Countercurrent ArchiMer
Qiu, Bo; Chen, Shuiming; Klein, Patrice; Sasaki, Hideharu; Sasai, Yoshikazu.
Located at the center of the western North Pacific Subtropical Gyre, the Subtropical Countercurrent (STCC) is not only abundant in mesoscale eddies, but also exhibits prominent submesoscale eddy features. Output from a 1/30 degrees high-resolution OGCM simulation and a gridded satellite altimetry product are analyzed to contrast the seasonal STCC variability in the mesoscale versus submesoscale ranges. Resolving the eddy scales of >150 km, the altimetry product reveals that the STCC eddy kinetic energy and rms vorticity have a seasonal maximum in May and April, respectively, a weak positive vorticity skewness without seasonal dependence, and an inverse (forward) kinetic energy cascade for wavelengths larger (shorter) than 250 km. In contrast, the...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Eddies; Instability; Mesoscale processes; Observational techniques and algorithms; Altimetry; Models and modeling; Ocean models; Variability; Seasonal variability.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00245/35588/34142.pdf
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The Vertical Structure of Large-Scale Unsteady Currents ArchiMer
Hochet, Antoine; Colin De Verdiere, Alain; Scott, Robert.
A linear model based on the quasigeostrophic equations is constructed in order to predict the vertical structure of Rossby waves and, more broadly, of anomalies resolved by altimeter data, roughly with periods longer than 20 days and with wavelengths larger than 100 km. The subsurface field is reconstructed from sea surface height and climatological stratification. The solution is calculated in periodic rectangular regions with a 3D discrete Fourier transform. The effect of the mean flow on Rossby waves is neglected, which the authors believe is a reasonable approximation for low latitudes. The method used has been tested with an idealized double- gyre simulation [performed with the Miami Isopycnal Coordinate Ocean Model (MICOM)]. The linear model is able...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Ocean dynamics; Rossby waves; Waves; Oceanic; Mathematical and statistical techniques; Fourier analysis; Models and modeling; Quasigeostrophic models.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00260/37081/35586.pdf
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Tracer stirring around a meddy: The formation of layering ArchiMer
Meunier, Thomas; Menesguen, Claire; Schopp, Richard; Le Gentil, Sylvie.
The dynamics of the formation of layering surrounding meddy-like vortex lenses is investigated using primitive equation (PE), quasigeostrophic (QG), and tracer advection models. Recent in situ data inside a meddy confirmed the formation of highly density-compensated layers in temperature and salinity at the periphery of the vortex core. Very high-resolution PE modeling of an idealized meddy showed the formation of realistic layers even in the absence of double-diffusive processes. The strong density compensation observed in the PE model, in good agreement with in situ data, suggests that stirring might be a leading process in the generation of layering. Passive tracer experiments confirmed that the vertical variance cascade in the periphery of the vortex...
Tipo: Text Palavras-chave: Circulation/ Dynamics; Advection; Dynamics; Atm/Ocean Structure/ Phenomena; Vortices; Models and modeling; Primitive equations model; Quasigeostrophic models; Tracers.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00255/36599/35160.pdf
Registros recuperados: 9
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